"I can confirm that the prince was admitted to Rikshospitalet today," palace information adviser Svein Gjeruldsen told Aftenposten.no on Tuesday evening.

Prince Sverre Magnus, born Dec. 3, 2005, had gastric flu last week and was admitted to the infant's ward at national facility Rikshospitalet on Tuesday a week ago. The new ailment is reportedly a respiratory infection.

"He has a respiratory infection, but this is completely undramatic," Gjeruldsen told Aftenposten.no.

Several vehicles attached to the palace could be seen parked outside Rikshospitalet on Tuesday evening. Crown Princess Mette-Marit arrived in a dark Volvo around 10 p.m., dressed in skiing clothes, her accompanying bodyguards were dressed in similar fashion.

According to Professor Dag Bratlid at St. Olav's Hospital in Trondheim, this is the season for such ailments.

"This virus often hits small children at this time of year. It causes the formation of mucus in the respiratory passages, and can cause children problems because they have narrow passages. In the worst case the virus can give real breathing problems of an asthmatic character," Bratlid said.

Prince Sverre Magnus was still in hospital on Wednesday morning.